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ICAL FIBER BASED LINE DIFFERENTIAL
PROTECTION ON SWITCHED COMMUNICATION
BACKBONE USING IEEE C37.94 STANDARD
SUCHARIT MONDAL, SOUVIK CHAKRABORTY, DIPANJAN DEB
TESTING & COMMISSIONING WING, TESTING DEPARTMENT
Abstract
The performance of the protection scheme for Extra High Voltage Lines is of paramount importance to ensure
the smooth operation of any power system, as experience shows that the Lines are most susceptible to faults.
Protection relays need to sense these faults and isolate the faulty sections within shortest possible time to avoid
the damage to plant and equipment due to the high fault current. Line Di erential relays are widely used as unit
protection in an interconnected EHV system for its simplicity and reliability. Utilities use communication schemes
for line di erential protection to enable the relay at one end of the line to communicate with the other end. This
needs continuous exchange of data between the relays at the two ends of the line through the communication
channel in order to assure correct operation of the protection scheme. Therefore, the communication channel
should always be in perfect condition in terms of availability, performance, quality and latency. In the past,
pilot wire communication or power line carrier communication was used as communication channel which was
vulnerable to electromagnetic interference. To get rid of this problem, electrical distribution utilities have moved
to optical fiber based digital communication to connect the line di erential relays at two ends.
With further advancement of technology, instead of using direct relay connection with dedicated optical fiber
only, we can now make another redundant path using devices employing IEEE C37.94 standard, to make the
line di erential protection even more reliable. In this paper, we will discuss the IEEE C37.94 standard and the
practical experiences that we have gained during its commissioning.
INTRODUCTION Two Main protections and one Backup protection are
used to form the protection backbone for 132 kV and 220
Like any Distribution utility, CESC has been adopting kV interconnectors.
modern technologies available across the globe for
protection of its Extra High Voltage (EHV) lines, which are Main-I Protection: Instantaneous type Optical Fiber /
critical element for any power system. Before going into Pilot based Line Differential protection
the details of IEEE C37.94 standard, which is implemented
in the CESC network for our EHV line protection, let’s Main-II Protection: Instantaneous type Optical Fiber /
delve into the general protection philosophy followed in Pilot based Line Differential protection and Distance
CESC system. protection with 3 time graded forward Zones. For short
length lines, distance protection is not used.
69
PROTECTION ON SWITCHED COMMUNICATION
BACKBONE USING IEEE C37.94 STANDARD
SUCHARIT MONDAL, SOUVIK CHAKRABORTY, DIPANJAN DEB
TESTING & COMMISSIONING WING, TESTING DEPARTMENT
Abstract
The performance of the protection scheme for Extra High Voltage Lines is of paramount importance to ensure
the smooth operation of any power system, as experience shows that the Lines are most susceptible to faults.
Protection relays need to sense these faults and isolate the faulty sections within shortest possible time to avoid
the damage to plant and equipment due to the high fault current. Line Di erential relays are widely used as unit
protection in an interconnected EHV system for its simplicity and reliability. Utilities use communication schemes
for line di erential protection to enable the relay at one end of the line to communicate with the other end. This
needs continuous exchange of data between the relays at the two ends of the line through the communication
channel in order to assure correct operation of the protection scheme. Therefore, the communication channel
should always be in perfect condition in terms of availability, performance, quality and latency. In the past,
pilot wire communication or power line carrier communication was used as communication channel which was
vulnerable to electromagnetic interference. To get rid of this problem, electrical distribution utilities have moved
to optical fiber based digital communication to connect the line di erential relays at two ends.
With further advancement of technology, instead of using direct relay connection with dedicated optical fiber
only, we can now make another redundant path using devices employing IEEE C37.94 standard, to make the
line di erential protection even more reliable. In this paper, we will discuss the IEEE C37.94 standard and the
practical experiences that we have gained during its commissioning.
INTRODUCTION Two Main protections and one Backup protection are
used to form the protection backbone for 132 kV and 220
Like any Distribution utility, CESC has been adopting kV interconnectors.
modern technologies available across the globe for
protection of its Extra High Voltage (EHV) lines, which are Main-I Protection: Instantaneous type Optical Fiber /
critical element for any power system. Before going into Pilot based Line Differential protection
the details of IEEE C37.94 standard, which is implemented
in the CESC network for our EHV line protection, let’s Main-II Protection: Instantaneous type Optical Fiber /
delve into the general protection philosophy followed in Pilot based Line Differential protection and Distance
CESC system. protection with 3 time graded forward Zones. For short
length lines, distance protection is not used.
69
